The treatment of patients having cancer frequently makes use of radiation therapy wherein radiation is directed to particular sites in the patient's body. These treatments require high precision, reliable and accurate patient set-up to position and immobilize the relevant portion of the patient's body undergoing the radiation. Various devices and equipment are available for effecting such action. For example, patient couches or tables are commonly provided at the radiation machine, e.g., linear accelerator, CT machine, MRI, etc., to support the patient in a prone or supine position while the relevant portion of the patient's body is held in a fixed or immobilized condition. To that end the immobilization of the relevant portion of the patient's body is commonly achieved by various types of devices mounted on the patient couch/treatment table.
A commonly used body part, i.e. the head, restraint device is a mask that is placed over the face of the patient to hold the patient's head stationary. Such masks may be molded to conform to the contours of the patient's face to ensure maximum immobilization. The back of the patient's head and/or contiguous portion of the patient's neck may be supported by a cushion which itself can be pre-contoured for a specific shape or can be conformed, e.g., molded, to the shape of the back of the patient's head. The mask itself can be pre-formed to a shape that will generally conform to the contours of the patient's face, or may be molded on the patient's face to closely conform to those contours. The molding of the mask is typically conducted preceding the first treatment. After this the mask can be mounted on the head of the patient and subsequently will be fixed to the patient support table. However, the patient's head and neck will still have to be supported, such as by cushions filled with granular material, for example, or by preformed cushions. Using cushions, deviations in the position of the head in relation to the preceding treatment can easily occur.
U.S. Pat. No. 5,702,406 discloses a reference system for noninvasive, stereotactic immobilization of a human head in reproducible position. The reference system comprises a head ring having a pair of support legs adapted to be positioned at opposite sides of the head of a specific patient. The reference system also comprises a mask containing a plurality of separate parts capable of assuming a given conformation. A first part is adapted to be conformed to and to cover the anatomical contours of a first area of the specific patient's head. A second part is adapted to be conformed to and to cover the anatomical contours of a second area of the specific patient's head which is not covered by the first part. The reference system further comprises means for connecting the mask parts with one another, said connection means also connecting the connected mask parts to the reference system. Another part of the reference system is a detachable support, made of plastic. The support is used during immobilization for supporting the back of the head of the patient. One of the disadvantages of this system is that the obtained mask has an open area on the cranial side and does not fully cover the head of a patient. Furthermore as mentioned above, the use of support leads to deviations in the position of the head in relation to the preceding treatment.
A disadvantage of the above described system resides in the use of a head support such as a support cushion. The use of said support to shape a mask adapted to a patient's head for instance, results in a mask which is adapted to the pre-shaped form of the support cushion. The obtained mask is hence not fully adapted to the anatomical contours of the body part that needs to be immobilized. In addition, the rotation of said body part will be adapted to the support cushion shape and material. This provides the patient with a very low comfort level especially if the treatment time is long.
Another disadvantage related to the use of a support cushion is the incapacity of the practitioner to be in touch with the body part surface which is supported by the support cushion. Hence, the practitioner will have a limited access to the body part surface supported by the support cushion which leads to a mask which is not fully conform to the anatomical contours of the mentioned body part. In case the practitioner has access to the body part surface which is supported by the support cushion of the prior art, he can ensure a perfect conformity of the mask to the anatomical contours and boney reference structures of the body part that needs to be immobilized. Moreover, the contact of the practitioner with the body part of interest will provide the patient with a security and a comfort feeling.
Still another disadvantage of the immobilization systems described in the prior art is that they comprise several devices that needs to be assembled which, on one hand, represents a high workload for the practitioner and on the other hand, prolongs the time required for the making of the immobilization mask thereby providing the patient with an uncomfortable feeling. The immobilization systems described in the prior art are also very bulky and a high amount of material is required for their manufacture which leads to a non-homogeneous dose delivery and high attenuation of the radiation beam.
The aim of the present invention is to provide a solution to overcome at least part of the above mentioned disadvantages. The invention thereto aims to provide a kit and a method, which are highly effective and easy to use and apply for the immobilization of a patient body part.